Opinions?
Also, I saw a review that said the LO would only be able to fit in the wrap for a few months (3-4). That true? My DS is already 2+, so I don't want to buy one for just a few weeks. I have an Ergo that I LOVE, but am looking for something a bit different to use on quick trips or walking around the house. Thanks!

Re: Moby vs. Sleepy Wrap
If you have the Ergo and you are happy with it I wouldn't get a Moby.
I know some people have mad ninja skills with the Moby to use it like a backpack but I've never been able to figure it out. It's kind of a pain to put on but really snug once it's on. We used it a ton from 1-3 months and occasionally until 5 months.
If you just want something quick and easy maybe a sling would be good? Those are easy to just throw in the diaper bag although they aren't comfortable for long periods.
We still use the Moby often for DD, but since I got a woven wrap, I've found myself using it more. I'm one of those ninjas who can get DD up into a back carry- it took a good couple of weeks to finally figure out!
Wovens can be used through toddlerhood, but, so can your Ergo.
I agree with pp though that if you love your Ergo, that's probably all you would really need. But if you want to get a wrap, if your DC is over 13 lbs already, I'd probably just get a woven, b/c it wouldn't be too long before you'd need something more supportive.